Asteroids

• Asteroids are found mostly between the orbits of Jupiter and Mars, while comets are found mostly between Venus and Mercury.
• Most asteroids lie in a vast ring between the orbits of Mars and Jupiter.
• Not everything in the main belt is an asteroid, for instance, comets have recently been discovered there, and Ceres, once thought of only as an asteroid, is now also considered a dwarf planet.
• Many asteroids lie outside the main belt, For instance, a number of asteroids called Trojans lie along Jupiter’s orbital path.
• Three groups — Atens, Amors, and Apollos — known as near-Earth asteroids orbit in the inner solar system and sometimes cross the path of Mars and Earth.

Meteoroid

• Asteroid: A relatively small, inactive, rocky body orbiting the Sun.
• Comet: A relatively small, at times active, object whose ices can vaporize in sunlight forming an atmosphere (coma) of dust and gas and, sometimes, a tail of dust and/or gas.
• Meteoroid: A small particle from a comet or asteroid orbiting the Sun.
• Meteor: The light phenomena which results when a meteoroid enters the Earth’s atmosphere and vaporizes; a shooting star.
• Meteorite: A meteoroid that survives its passage through the Earth’s atmosphere and lands upon the Earth’s surface.

Kuiper Belt

• The Kuiper Belt (also known as the Edgeworth–Kuiper belt) is a region of the Solar System that exists beyond the eight major planets,
• It extending from the orbit of Neptune (at 30 AU) to approximately 50 AU from the Sun. (1 Astronomical Unit (AU) = distance between the Earth and the Sun)
• It is similar to the asteroid belt, in that it contains many small bodies, all remnants from the Solar System’s formation.
• Ultima Thule is a Kuiper Belt object it was discovered by the Hubble Space Telescope in 2014.
• Ultima Thule will be the farthest object ever visited by a spacecraft.

Habitable-zone Planet Finder (HPF)

• HPF is an astronomical spectrograph, installed on the 10m Hobby-Eberly Telescope at McDonald Observatory (US).
• The HPF searches for exoplanets by using the Doppler effect.
• The HPF provides the highest precision measurements of infrared signals from nearby low-mass stars, and astronomers use it to validate the candidate planet by excluding all possibilities of contaminating signals to a very high level of probability.
• It is designed to detect and characterise planets in the habitable-zone also known as ‘Goldilocks zone’- the region around the star where a planet could sustain liquid water on its surface.
• The Habitable-zone Planet Finder (HPF) has confirmed its first planet (exoplanet) called G 9-40b.

Neutron Stars

• Neutron stars comprise one of the possible evolutionary end-points of high mass stars.
• Once the core of the star has completely burned to iron, energy production stops and the core rapidly collapses, squeezing electrons and protons together to form neutrons and neutrinos.
• A star supported by neutron degeneracy pressure is known as a ‘neutron star’, which may be seen as a pulsar if its magnetic field is favourably aligned with its spin axis.